Micromechanical rate-of-rotation sensors are known from the prior art, wherein it may, in general, be distinguished between decoupled and coupled sensors. In decoupled sensors, the vibrating structure comprises a drive means and a detection element which is mechanically separate therefrom. The drive means is brought into a usually stationary state of movement, i.e. the drive oscillation. Spreading of the drive oscillation to the detection element is prevented by a suitable arrangement of spring elements coupling the drive element to the detection element. If a rate of rotation acts upon the sensor from outside, the drive element is excited to a further movement, i.e. the detection movement, besides the drive oscillation. In further consequence, said movement is transferred to the detection element via the spring elements, monitored and evaluated.
In coupled sensors, the vibrating structure has the function of both, a drive element and a detection element. Said vibrating structure may be realized both in one piece and a number of pieces, is excited to a drive oscillation and also carries out the detection movement, besides the drive oscillation, when an external rate of rotation acts upon it.
Coupled micromechanical movement sensors comprising a wing-shaped detection unit are known from DE 103 20 725 A1 and DE 199 15 257 A1. Said detection unit is centrally mounted on a substrate. The central mounting is carried out by means of a number of radially distributed suspension beams, each being aligned transversely to the tilting direction to be detected, which suspension beams are mounted to one central point or a number of decentralized points on the substrate.
Due to an excitation generated internally in the sensor, the detection unit performs a rotational oscillation, as the drive movement, in parallel with the substrate and about a center of rotation coinciding with the central mounting. As a result of an external rate of rotation acting upon the sensor (in the direction of or about the sense axis) and Coriolis forces generated thereby, the detection unit experiences a change in angular momentum resulting in a tilting movement thereof about an axis (detection axis) perpendicular to the axis of rotational oscillation/drive axis and to the exterior rate of rotation. The tilting movement is detected by means of a capacitive sensor arrangement which is formed by the detection unit, on the one hand, and capacities located opposite said detection unit on the substrate, on the other hand. The sensor arrangement is realized by a plurality of capacities arranged in a distributed manner in order to enable detection depending upon the direction of the rate of rotation.
For adjusting sensitivity of the response behavior in various directions, DE 199 15 257 A1 discloses suitable dimensioning of the aspect ratio of the suspension springs or beams of the detection unit. By purposefully realizing the aspect ratio of suspension beams arranged in specific directions in space, for example, rotational oscillation (drive oscillation) of the detection unit about the drive axis and tilting about a detection axis perpendicular to the drive axis may be enabled, whereas tilting about a sense axis perpendicular to said axes may be substantially prevented or restricted in a desired manner.
Even though detection of rates of rotation in a manner specific to the direction of the rate of rotation is possible in this way, sensors known from the described prior art are susceptible to the influence of external disturbances, such as shock acceleration or vibrations, and often not robust enough due to their central suspension. Thus, pronounced relative changes in position between detection unit and substrate may occur, which may in turn result in a so-called sticking and uselessness of the sensor.